Incidentally, I'm planning on adding solitaire as the next game!
Also, I was just checking around to see if there were any good methods for telling if a puzzle is solvable without solving it. Seems geeks for geeks have some code for it.
https://www.geeksforgeeks.org/dsa/check-instance-15-puzzle-s... The only other solution I can think of is detecting both configurations (blank in bottom right or top left) and displaying something when either is reached.
Half of the random states created are solvable, and the other half are unsolvable.
My solution was not checking if the puzzle is solvable (the mathematics of this seem complicated), but starting with a solved one and then do a fixed number of random movements.
But sheesh! The first time I play the numbers puzzle on a computer in my life, and the first time in 30 years that I play it at all, and I find out some joker has snapped two of the pieces out and reversed them, making it unsolvable?! Diabolical!
Cool stuff though!